title: Intracellular fate of carbon nanotubes inside murine macrophages: pH-dependent detachment of iron catalyst nanoparticles.
abstract: BACKGROUND
  Carbon nanotubes (CNT) are a family of materials featuring a large range of length, diameter, numbers of walls and, quite often metallic impurities coming from the catalyst used for their synthesis. They exhibit unique physical properties, which have already led to an extensive development of CNT for numerous applications. Because of this development and the resulting potential increase of human exposure, an important body of literature has been published with the aim to evaluate the health impact of CNT. However, despite evidences of uptake and long-term persistence of CNT within macrophages and the central role of those cells in the CNT-induced pulmonary inflammatory response, a limited amount of data is available so far on the CNT fate inside macrophages. Therefore, the overall aim of our study was to investigate the fate of pristine single walled CNT (SWCNT) after their internalization by macrophages.
  
  
  METHODS
  To achieve our aim, we used a broad range of techniques that aimed at getting a comprehensive characterization of the SWCNT and their catalyst residues before and after exposure of murine macrophages: X-ray diffraction (XRD), High Resolution (HR) Transmission Electron Microscopy (TEM), High Angle Annular Dark Field-Scanning TEM (HAADF-STEM) coupled to Electron Energy Loss Spectroscopy (EELS), as well as micro-X-ray fluorescence mapping (μXRF), using synchrotron radiation.
  
  
  RESULTS
  We showed 1) the rapid detachment of part of the iron nanoparticles initially attached to SWCNT which appeared as free iron nanoparticles in the cytoplasm and nucleus of CNT-exposed murine macrophages, and 2) that blockade of intracellular lysosomal acidification prevented iron nanoparticles detachment from CNT bundles and protected cells from CNT downstream toxicity.
  
  
  CONCLUSIONS
  The present results, while obtained with pristine SWCNT, could likely be extended to other catalyst-containing nanomaterials and surely open new ways in the interpretation and understanding of CNT toxicity.
authors.affiliation: Inserm U955 Équipe 4, Faculté de Médecine, 8 rue du Général Sarrail, 94010 Créteil, France.
authors.forename: Cyrill
authors.initials: C
authors.lastname: Bussy
authors.forename: Erwan
authors.initials: E
authors.lastname: Paineau
authors.forename: Julien
authors.initials: J
authors.lastname: Cambedouzou
authors.forename: Nathalie
authors.initials: N
authors.lastname: Brun
authors.forename: Claudie
authors.initials: C
authors.lastname: Mory
authors.forename: Barbara
authors.initials: B
authors.lastname: Fayard
authors.forename: Murielle
authors.initials: M
authors.lastname: Salomé
authors.forename: Mathieu
authors.initials: M
authors.lastname: Pinault
authors.forename: Mickaël
authors.initials: M
authors.lastname: Huard
authors.forename: Esther
authors.initials: E
authors.lastname: Belade
authors.forename: Lucie
authors.initials: L
authors.lastname: Armand
authors.forename: Jorge
authors.initials: J
authors.lastname: Boczkowski
authors.forename: Pascale
authors.initials: P
authors.lastname: Launois
authors.forename: Sophie
authors.initials: S
authors.lastname: Lanone
mesh_terms: D000818:Animals; D002401:Cathepsin B / Q000378:metabolism; D002460:Cell Line; D006863:Hydrogen-Ion Concentration; D058085:Iron Compounds / Q000378:metabolism* / Q000633:toxicity; D051907:Lysosomal Membrane Proteins / Q000378:metabolism; D008247:Lysosomes / Q000378:metabolism; D018942:Macrolides / Q000494:pharmacology; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism*; D053768:Metal Nanoparticles; D051379:Mice; D046529:Microscopy, Electron, Transmission; D037742:Nanotubes, Carbon / Q000032:analysis* / Q000633:toxicity; D013052:Spectrometry, X-Ray Emission; D046590:Spectroscopy, Electron Energy-Loss; D017356:Synchrotrons; D014961:X-Ray Diffraction; D052118:Lysosomal-Associated Membrane Protein 1
chemical_list: D002401:Cathepsin B; D058085:Iron Compounds; D051907:Lysosomal Membrane Proteins; D018942:Macrolides; D037742:Nanotubes, Carbon; C052255:Lamp1 protein, mouse; D052118:Lysosomal-Associated Membrane Protein 1; C515100:iron pentacarbonyl; C036978:concanamycin A; C533915:Ctsb protein, mouse